My kitchen has a very similar layout. Here is what we did. I also think my backsplash, or something similar would work for you.

More than anything else, your kitchen needs better lighting. Under cabinet lighting will put the light directly on your work surface, as well as cast a warming glow to the space. You also need some recessed lights to brighten up the dark wood surfaces and to give better general lighting. A nice pendant above the island instead of a central flush fixture would be the finishing touch. Once you can see all of the colors and details that are in your kitchen, you will be able to appropriately choose a backsplash that will look good with all of the different elements. Poor lighting changes the color perception of many things.

I would pick out one of the colors in your granite and match to that...looks like it would be the gold/creamy yellow beige family..... If you have some sample granite take it with you tile shopping and bring home samples to see how they look in your lighting.....after the BS is in pick a coordinating color for the walls.

I'm not sure you need a backsplash. You already have the four inch backsplash.
I would just change the paint color to be more on tone with your granite.

Usually this board is great with backsplash suggestions.

Teachertile: yours look great and seems like something similar would work for the OP. But, I agree to get some UCL first and see what you think at that point.

Backsplashes are relatively permanent and expensive. If you already know you want to paint the walls a lighter neutral, I think that (and the ucl) should happen first or at the same time. I think teachertile's looks so nice because the paint and backsplash are working with the counter.